Which diagnostic test is used for suspected tinea capitis?

Which diagnostic test is used for suspected tinea capitis?

• A. Wood lamp
• B. KOH prep
• C. Gram stain
• D. Patch testing

Answer: (B)

Identifying fungal elements directly in the scalp hair or scales is the essential approach for suspected tinea capitis. A potassium hydroxide (KOH) preparation is used because KOH dissolves keratin and clears the debris, making fungal hyphae and spores visible under light microscopy. This provides rapid, in-office confirmation of a dermatophyte infection and guides timely treatment. Wood lamp examination can help in certain dermatophyte infections that fluoresce under UV light, but many species do not fluoresce and sensitivity is inconsistent. So it cannot be relied on alone for diagnosing tinea capitis. Gram staining focuses on bacteria and isn’t useful for diagnosing fungal infections of the scalp. Patch testing is used for allergic contact dermatitis, not fungal infections. If a precise organism is needed, culture or molecular methods can be used, but the KOH prep is the quickest and most practical initial test.

Identifying fungal elements directly in the scalp hair or scales is the essential approach for suspected tinea capitis. A potassium hydroxide (KOH) preparation is used because KOH dissolves keratin and clears the debris, making fungal hyphae and spores visible under light microscopy. This provides rapid, in-office confirmation of a dermatophyte infection and guides timely treatment.

Wood lamp examination can help in certain dermatophyte infections that fluoresce under UV light, but many species do not fluoresce and sensitivity is inconsistent. So it cannot be relied on alone for diagnosing tinea capitis. Gram staining focuses on bacteria and isn’t useful for diagnosing fungal infections of the scalp. Patch testing is used for allergic contact dermatitis, not fungal infections. If a precise organism is needed, culture or molecular methods can be used, but the KOH prep is the quickest and most practical initial test.